a) Technical Field of the Invention
The present invention relates to a wrench structure, and in particular, to a ratchet wrench capable of providing high torque movement.
b) Description of the Prior Art
As shown in FIG. 1, a common conventional wrench 10 has a plurality of engaging notches 11 formed as one unit with the wrench 10 and the notches 11 moves together with the wrench 10 to rotate a nut 12. When the wrench 10 is rotated to a certain degree, as a result of restriction by object around the wrench 10, the wrench 10 has to be lifted up and placed at the original position and then repeat the process in order to rotate the nut 12. As a result of repeating engagement and disengagement of the wrench 10 with the nut 12, the notch 11 of the wench 10 is often dislocated in the process of tightening or loosening of the nut 12.
FIG. 2 is another prior art wrench 10 having a bent structure to provide convenient holding of the handle of the wrench 10 by a user. However, this type of wrench 10 has the drawback as that of FIG. 1 and the wrench 10 is often dislocated from the nut 12. Besides, the process of tightening and loosening of nut 12 by using this wrench 10 is slow.
FIGS. 3 and 4 show another types of wrench 20 having a head portion being provided with a circular opening 201 to contain a ratchet wheel 21. A cavity 202 is provided to the circular opening 201, adjacent to the one lateral side of the rod body to contain a restrictive teeth structure 22 and a spring 23. If the ratchet wheel 21 is to rotate clockwise, as the teeth of the ratchet wheel 21 is in engagement with that of the restrictive teeth structure 22, and one side of the restrictive teeth structure 22 is restricted by the wall of the cavity 202, thus, the ratchet wheel 21 cannot rotate clockwise, but the wrench 20 can rotate clockwise to drive the ratchet wheel 21 to rotate the nuts. If the ratchet wheel 21 rotates counterclockwise, as the teeth of the ratchet wheel 21 is in engagement with that of the restrictive teeth structure 22, and one side of the restrictive teeth structure 22 is restricted by the spring 23 and the spring 23 is compressible, thus, ratchet wheel 21 can rotate freely in a counterclockwise direction, and t e eth-skidding is resulted by the teeth of the restrictive teeth structure 22 with that of the ratchet wheel.
The advantage of this wrench 20 is no repeating of engagement and disengagement of the nut 12 with the wrench 20, and the operation of the wrench 20 is faster. However, if a reverse direction of the nut is required, the wrench 20 has to be changed to another face such that the ratchet wheel 21 can be rotated in a reverse direction. In view of the need of reversing the rotation of the wrench 20, it cannot be made into the shape of the wrench 10 as shown in FIG. 2 to provide a bent angle so that the application of the wrench 20 is smooth. The drawback is also found in U.S. Pat. No. 5,636,557.
FIG. 5 is another ratchet wrench 30 having a ratchet wheel 31 provided with a restrictive teeth structure 32. Two sides of the restrictive teeth structure 32 are provided with teeth for the engagement with that of the ratchet wheel 31. The restrictive teeth structure 32 can rotate about a center to a certain degree. The restrictive teeth structure 32 causes the ratchet wheel 31 to produce a single direction rotation. If frequent reverse of direction of rotation is required, the restrictive teeth structure 32 rotates to a certain angle about the center, and at this instance, the teeth at one side of the restrictive teeth structure 32 can engage with the teeth of the ratchet wheel 31 and the restrictive teeth structure 32 causes the ratchet wheel 31 to produce a free rotation. Thus, the rotation of the restrictive teeth structure 32 is used to cause a change of rotation direction. Thus, the wrench having multiple angle shown FIG. 2 can be fabricated. However, this design has other drawback. The engagement of the restrictive teeth structure 32 and the ratchet wheel 31 is depend on a few teeth to provide rotation, if the torque is too great, the restrictive teeth 32 or the engaged teeth of the ratchet wheel 31 may be damaged. U.S. Pat. Nos. 5,884,538, 5,626,062 and 5,782,147 disclose this type of wrench.
U.S. Pat. Nos. 5,533,427 and 5,230,262 provides the advantages that shown in FIGS. 3 and 5. In U.S. Pat. No. 5,533,427, the ratchet wheel 40 of the disclosed wrench 10 is in engagement with the restrictive teeth structure 50 which can resist a larger torque. By using the reverse direction control 60,70, the position of the engagement of the restrictive teeth structure 50 with that of the ratchet wheel 40 is changed so as to change the rotation direction of the ratchet wheel 40. Unlike the wrench in FIG. 3, a reverse of the wrench is required. The wrench 10 can be made into a shape as shown in FIG. 2 to provide smooth use for the user. However, the drawback of such wrench 10 is that the head portion 20 is larger than that shown in FIG. 3 for the reason that the head portion 20 is used to contain the ratchet wheel 40, a directional control 60 and the restrictive teeth structure 50. The design principle of U.S. Pat. No. 5,230,262 is similar to that of U.S. Pat. No. 5,533,427. These two patents disclose wrenches with high torque.